In wireless communication networks information about the format in which the data is communicated between network nodes, such as between a terminal device (which is a wireless terminal device, being mobile or fixed, e.g. a UE in a LTE network) and a base station (such as a eNB), is transmitted as control information in a specified and known way.
The 3rd-Generation Partnership Project (3GPP) has developed standards for a fourth-generation wireless communications technology referred to as “Long Term Evolution” (LTE) or, more formally, the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). In an LTE network, the Physical Downlink Control Channel (PDCCH) and the Enhanced Physical Downlink Control Channel (ePDCCH) are physical downlink control channels used to send downlink and uplink grants, which are specifications indicating to the UE, respectively, how transmissions to the UE on the Physical Downlink Shared Channel (PDSCH) are formatted and how transmissions from the UE on the Physical Uplink Shared Channel (PUSCH) should be formatted. On PDSCH and PUSCH, both control data and user data are multiplexed by the Medium Access Control (MAC) layer, and thus these physical data channels may be understood to carry Layer 2 messages. However, some uplink control messages (i.e., uplink control information, or UCI), such as downlink hybrid automatic repeat request (HARQ) feedback and channel state information (CSI) reports, are either sent on the Physical Uplink Control Channel (PUCCH) or are multiplexed by the physical layer on the PUSCH resource, in which case the PUSCH is rate matched around the UCI. The terminal device (UE) first decodes the control information (grant) that contains information on the transport format of the transmitted (downlink) data or the data to be transmitted (uplink).
In LTE networks, for example, the grant is transmitted on PDCCH or ePDCCH, as explained above, using a variety of DCI formats which are specific to different operating modes of the terminal device (UE). The size of the PDCCH can dynamically be adopted using an indicator transmitted on PCFICH which is read by UEs to determine in which symbol the control channel (PHCCH) ends and the data channel PDSCH starts. Hence, the PCFICH provides a configuration of the PDCCH, i.e. where to find the PCCH, In case the ePDCCH is used, then the control region for providing DCI is pre-configured and the UE perform a rate-matching, i.e. an adjustment of the coding rate, for example by taking into account, e.g., channel quality and available resource elements, around the ePDCCH if it detects a grant on the ePDCCH. This means that resource elements used by any ePDCCH (present or not present) on the resource pre-configured for ePDCCH are not used for PDSCH.